PBX systems attempt to keep track of telephone calls placed using the PBX system through the use of station message detail recording systems (SMDR systems). In summary, most SMDR systems record the trunk and extension used for the placement of a call as well as the duration of the call and, the destination number of the call. In many circumstances, the SMDR information must be used to bill for calls placed using the PBX system. For example, in a hotel environment, the only information that the hotel ownership has as to long distance traffic associated with a particular patron of the hotel will be through the SMDR data received from the hotel's PBX system. Unfortunately, SMDR data is extremely inaccurate as to the duration of the call. Virtually all present PBX systems use extremely simple algorithms for determining the completion of a call which can result in both overcharging and undercharging for long distance calls based on inaccuracies in the timing of the calls.
Recent developments in localized answer detect methodology and technology have allowed the development of sophisticated call processing systems which can be situated on the trunk lines between the PBX system and the central office of the telephone company. One such system is the IntelliMax.TM. system manufactured by Intellicall, Incorporated. These systems can accurately determine the duration of long distance telephone calls as well as recording other information relevant to the amount to be charged for a particular call. However, these systems cannot determine the particular extension from which the call was placed if they are placed on the trunks between the PBX system and the central telephone office. Accordingly, a need has arisen for a system which can receive SMDR serial data from a PBX system and call record data from a call processing system and merge these two sets of data to create an accurate record of telephone calls placed using the PBX and call processing systems which includes the extension number from which the call was placed. In addition, the merged data set associated with a particular telephone call must include the accurate duration of the call measured by the call processing system.